While plans were to install the wideband into our C6's exhaust prior to performing any modifications (so that each part's effect on air-fuel ratio could be assessed), extenuating circumstances meant we weren't able to get it up and running prior to installing our CORSA exhaust. However, CORSA - as well as other exhaust manufacturers and independent tuners we've spoken to-has assured us that a cat-back exhaust system alone, no matter its flow capacity, will not alter the LS2's air-fuel ratio in any appreciable way. "The installation of the exhaust itself should not alter the OE computer tune at all, and the AFR map for the car should stay exactly the same," says CORSA'S ED BURGY. "The difference is that the engine is now breathing more efficiently. What that means is that since it is now easier for the engine to get rid of the spent air-fuel mixture from the combustion chambers, there is more empty volume in the chambers to be filled with fresh air and fuel on the intake cycle; more air and fuel (even at the same AFR) will translate into more horsepower. That said, the new efficiency of our exhaust does provide an opportunity for a more aggressive or performance-oriented tune to be placed into the computer and deliver even better results."
This will ring even more true when we perform more heavy engine-related mods in the future, where the unrestricted flow of CORSA'S dual 3-inch exhaust will pay even larger power dividends. Look for these mods in upcoming issues-and as of this writing, our LC-1 is wired and ready, set to help us monitor our progress and assess the need for custom tuning along the way.
Now, with the muffler/over-axle-pipe assemblies hanging semi-loose, detach the two brackets at the rear of each. Do this one side at a time-one entire muffler/pipe assembly can come out while the other is left intact. While it may be possible to slip the hangars out of the rubber, we opted to simply unbolt the entire bracket assemblies from the frame. This is easily done with a 13mm open end (a ratcheting one helps). | 
Have a hand ready to hold the muffler, as with the two brackets at the rear gone, there's nothing else holding it to the car. Note also that the over-axle pipes come welded to the mufflers, which is apparently why some exhaust installers think these pipes must be cut. To get the muffler/pipe assembly out, use your other arm (or better yet, an assistant) and carefully begin to snake the over-axle pipe rearward, being mindful of wiring and other items above the axle area. | 
We were surprised to find a simple sideways twist will allow each muffler/over-axle-pipe assembly to come out intact and without drama-no sawzall needed. There's plenty of room, and you won't even have to unbolt the anti-roll bar! And while it doesn't look it from the angle this photo is taken, you really can take one side out while the other hangs intact. |
If you haven't done so already, pull the rubber hangar assemblies off the back of the mufflers; they'll be reused. Obvious in this photo is how GM sprays each muffler with black paint in the portion visible from outside the car. Will our Corsa mufflers, with their shiny luster, look out of place hanging beneath our Monterey Red machine? | 
A peek through the inlet of the CORSA Power-Pulse Reflective Sound Cancellation (RSC) muffler reveals a secret to its awesome flow: it's absolutely a straight shot through! This doesn't mean these patented mufflers are nonfunctional, however; though hard to pick out here, there are passages leading perpendicular to the exhaust path near the muffler's inlet. Sound waves entering these passages encounter chambers where they are reflected 180 degrees out of phase and back out, canceling themselves and other sound waves traveling through the exhaust. The geometry of the chambers is specifically designed to deal with the sound frequencies responsible for the annoying drone exhibited by other types of mufflers, yet leave the good sounds intact. | 
After transferring the hangar assemblies to the CORSA mufflers, put a muffler loosely in place by partially installing the hangar bolts to the body. In this way, the muffler casing will rest on the anti-roll bar (which is skimpier on our vehicle than for Z51-equipped cars). Then slide in an over-axle pipe from ahead of the axle, being sure to slip a clamp on the end before doing so. Note: to determine which over-axle pipe is which, just match the contours with the stock system. Trial fitting each in place will also make it obvious, since the front of each pipe must face toward the center of the car. Also, note that the mufflers are different, with each having its inlet more toward the outside of the car. |